This document provides an overview of different types of fasteners including materials, corrosion resistance properties, drive types, head styles, measurements, and grades. Some key points covered include: - Common fastener materials include alloy steel, brass, bronze, chrome/nickel-plated steel, stainless steel, galvanized steel, and zinc-plated steel. Materials vary in corrosion resistance and cost. - Drive types for installing fasteners include Phillips, Frearson, Pozidriv, slotted, hex socket, Torx, and square drives, each with advantages and limitations. - Head styles include hex, pan, flat, round, oval, truss, socket, and button heads

1. Fastener Basics
Copyright © 2000-2013 Bolt Depot Inc.Page 1
Alloy steel is highly
hardened and usually
black oxide and/or oil
coated,offering little
corrosion resistance.
Brass and bronze are
copper alloys with good
corrosion resistance.
More expensive than
steel,these materials are
typically used for
decorative applications.
Colors can vary signifi-
cantly.
Chrome and nickel
plated steel are smooth
and polished for
appearance.The plating
offers moderate corro-
sion resistance.
Stainless steel offers
good corrosion
resistance,making it
suitable for outdoor and
marine applications,but
is more expensive than zinc plated.
Hot-dipped galvanized
steel has a thicker zinc
coating for better
corrosion resistance,
making it suitable for
outdoor use.Because of the thick plating,only
galvanized nuts and washers will fit galvanized
bolts.The coating typically has a rough,dull grey
finish.
Zinc-plated steel is a
low carbon steel for
general use.Relatively
inexpensive,with the
zinc plating providing
moderate corrosion
resistance suitable for
indoors or otherwise dry
conditions.Color is
either a blue-ish tint or yellow depending on the
exact process.
Note: Do not rely on this guide for color-matching.
The appearance of these materials sometimes differs
significantly from the photos below.
Fastener Grade (US) or Class (metric) refers to the mechanical properties
of the fastener material.Generally,a higher number indicates a stronger,
more hardened (but also more brittle) fastener.
For a chart of fastener grades,head markings and mechanical properties,see Bolt
Depot’s Grade markings and Strength Chart at http://boltdepot.com/info
Note: In addition to these markings,the head will often have a manufacturer stamp.
Grade 2 Grade 5 Grade 8 Class 8.8 Class 10.9 Class 12.9
US bolt head markings Metric bolt head markings
8.8 10.9 12.9
Hex bolts, or hex cap screws,are used in machin-
ery and construction.Can be used with a nut,or
in a tapped hole.Fully threaded hex bolts are
also known as tap bolts.
Wood screws have large threads and a smooth
shank for pulling two pieces of material
together.They can be used in wood and other
soft materials.
Sheet metal screws have sharp points and
threads,and are designed to be driven directly
into sheet metal.They can also be used in softer
materials like plastic,fiberglass,or wood.
Machine screws are fully treaded for use with a
nut or in a tapped hole.Certain types are
sometimes referred to as stove bolts.
Socket screws are machine screws with an
internal hex socket (Allen) drive.Longer lengths
may have a smooth shank.
Lag bolts,or lag screws,are large wood screws
with hex heads.Typically used for wood
construction and landscaping.
Nuts are used to fasten machine threaded
fasteners in through-hole applications.Lock nuts
help prevent loosening.
Washers spread the load over a greater surface
area when tightening a bolt,screw or nut.Lock
washers help preventing loosening.
Tip: Find a more comprehensive fastener type chart at http://boltdepot.com/info
Carriage bolts have smooth,domed heads with
a square section underneath that pulls into the
material to prevent spinning during installation.
Fastener MaterialsCommon Fastener Types
Grade / Class and Fastener Strength

2. Copyright © 2000-2013 Bolt Depot Inc.Page 2
Machine screws, Phillips pan head, Stainless steel 18-8, #12-24 x 1"
Fastener type Material Diameter
Thread Count (TPI)
Length
Phillips
Frearson
Pozidriv
Slotted
Combo
Hex socket
(Allen)
Square
(Robertson)
Torx
Phillips and Slotted
drives are common in
screws,but prone to
cam-out (stripping).
Combo drives,that
can be used with
either driver,are
available for many
fastener types.
Frearson and Pozidriv
are similar to Phillips,
but less prone to
cam-out.
Hex socket (Allen)
drives are compact
and easy to drive,but
prone to cam-out.
Torx and Square drive
are resistant to
cam-out and can be
installed single-
handed.
Note: Most drive types
(Frearson and Slotted
being notable exceptions)
require the correct driver
size for proper installation.
Hex heads are typically used
with larger bolts and screws,
and tightened with a wrench.
Pan heads have a slightly
domed head that sits above
the surface.
Flat heads are installed in a
countersunk hole for a flat
surface.
Round heads are tall domed
heads,used primarily for
decorative purposes.
Oval heads are a low domed
and countersunk heads,used
primarily for decorative
purposes.
Truss heads are slightly
domed,with a wide head for
an extra large surface area.
Socket heads are narrow
with a socket drive,and
knurled or smooth sides.
Button heads feature a
medium dome.Typically used
with a hex socket drive.
Machine threaded fasteners specify a thread density
in Threads Per Inch (US) or as a Thread Pitch in
mm (Metric).
For a given diameter,a fastener may be available in
coarse (standard),fine and sometimes super fine
thread.
Fastener length is
usually measured from
where the material is
assumed to be to the
end of the fastener.
Thus,countersunk fasteners
are measured overall and
non-countersunk fasteners
are measured from under
the head.
For most
types of
fasteners,the
diameter is
measured on
the outside of
the threads.
Note:US diameters under 1/4”are given as numbers
(e.g.#12) instead of inches,in order of increasing size.
If you need to find the actual diameter,use a table
corresponding to your fastener type at
http://boltdepot.com/info
Different washer patterns have different outside
diameters. For example,hardened US washers are
available in USS (wider) and SAE (narrower) patterns.
Fender washers have large outside diameters.
Nut and washer sizes indicate the screw or bolt they fit. For example:
3/8”-16 Hex Bolt 3/8” Washer 3/8”-16 Nut
1/4”
SAE
1/4”
USS
1/4”x 1”
Fender
• In-depth fastener info
• Charts and tables
• Printable lay-over charts
and tools for quickly
identifying fastener sizes
and types
• Much more...
At http://boltdepot.com/info you'll find:
Nut and Washer Sizes
How Fasteners are Notated: An Example
Drive Types Head Styles Measuring Diameter
Thread Count and Thread Pitch
Measuring Length
More Information